Evolution of Bars Katherine Xiang, Johns Hopkins University supervised by Dr. David Nataf & in Galaxies Professor Lia Athanassoula, Aix-Marseille Universite July 28th, 2018 NGC 1300 NGC 1672 Images taken by the Hubble Space Telescope. Background: Bar formation • Roughly 60% of spiral galaxies have bars (Buta et al., 2010) • Significant proportion of all galaxies • The Milky Way and Andromeda both have bars • Bar formation is a cornerstone of galaxy evolution • Bars form when instabilities cause deviation of orbits from circular paths (Athanassoula, 2005) N-body simulation specifics Face-on • N-body model used was developed by our collaborator Lia Athanassoula 1. Luminous disk, 200,000 particles • Initialized w/ exponential drop-off radially, and a sech2 drop-off in the z-axis 2. Dark matter halo, 1,000,000 particles • Parameterized by halo scale lengths with a drop-off with radius squared • Looking for kinematic signatures of a bar in the buckling phase, which is when the bar begins extending out of its galactic plane • Want to eventually catch a bar buckling, observationally How do bars form? From 3D N-body simulations: 1. A weak, thin bar forms and sits within its galactic plane 2. The bar becomes unstable: it buckles and settles with an increased thickness and velocity dispersion A. During the buckling process, the bar is N/S asymmetric B. The N and S portions do not necessarily buckle at the same time 3. When seen edge-on, the bar is visibly thicker than its galactic plane, and appears boxy or peanut shaped 1 2 3 Edge-on Edge-on • Martinez-Valpuesta et al., 2006. Signatures of the buckling instability Face-on 2D plots of line-of-sight velocity Edge-on Face-on Observations • MaNGA: Mapping Nearby Galaxies at APO, survey of 5000 galaxies, 800+ barred spiral galaxies • ≈ 30 almost exactly face-on barred galaxies, statistically • ≈ 350 that are ‘close enough’ to face-on Image: Dana Berry / SkyWorks Digital Inc., David Law, and the SDSS collaboration Face-on, simulation Observations & Unsharp Masking (cont’d) Thank you! .